Transmission apparatus, transmission method, reception apparatus, reception method, program, and broadcasting system

ABSTRACT

Disclosed herein is a transmission apparatus for transmitting AV (Audio/Video) content, including: an acquirer configured to acquire an estimated number of audience terminals indicative of an estimated number of reception apparatuses receiving the AV content; a computer configured, in conjugation with the AV content, to compute, on the basis of the estimated number of audience terminals, a validity probability of trigger information associated with control of an application program to be executed in the reception apparatus; a generator configured to generate the trigger signal including the computed validity probability; and a transmitter configured to transmit the generated trigger information with the AV content.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of ProvisionalApplication Ser. No.

61/378,256, filed Aug. 30, 2010, the entire contents of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transmission apparatus, atransmission method, a reception apparatus, reception method, a program,and a broadcasting system and, more particularly, to a transmissionapparatus, a transmission method, a reception apparatus, receptionmethod, a program, and a broadcasting system that are configured tocontrol, from the transmission side of digital television broadcasting,an access operation of the reception side to a predetermined server.

2. Description of the Related Art

In these days, digital television broadcasting has been promoted inJapan, resulting in the popularization of terrestrial digitalbroadcasting and BS (Broadcast Satellite) digital broadcasting, forexample. With digital television broadcasting, such as terrestrialdigital broadcasting, so-called data broadcasting has been realized inaddition to program broadcasting. The content carried by this databroadcasting allows the displaying of the information associated withon-air programs as well as the information (announcement of otherprograms, news, weather forecast, traffic information, and so on) notassociated with on-air programs (refer to Japanese Patent Laid-Open No.2006-50237 below).

It should be noted that, in the data broadcasting in Japan, a banddedicated to data broadcasting was allocated in advance within thebroadcasting band for digital television broadcasting at the timetelevision broadcasting was digitalized. The data broadcasting of Japanwas realized by broadcasting data broadcast content by use of thisdedicated band.

On the other hand, the digital television broadcasting in the USA has noallocation of such a band dedicated to data broadcasting as the Japanesecounterpart.

To be more specific, a broadcasting band for the current Americandigital television broadcasting is occupied by a video band, an audioband, and a control information band, so that no band is allocated todata broadcast content as shown in FIG. 1A. Therefore, the allocation ofthe band for broadcasting the content for data broadcasting to thelimited broadcasting band for digital television broadcasting mustnarrow the video band and the audio band as shown in FIG. 1B, forexample.

SUMMARY OF THE INVENTION

However, the narrowing of the video band and the audio band to allocatea band for broadcasting the content for data broadcasting does not leadto a realistic solution because of the inevitable deterioration in thepicture and tone qualities of television programs.

In addition, even if the band for data broadcasting content can beallocated, the data volume that can be transmitted in band thusallocated is necessarily limited. This presents problems that theinformation volume of data broadcasting content runs low and an attemptto increase the information volume increases the time for the receptionside to receive necessary data.

In order to overcome the above-mentioned problem, a method of supplyingdata broadcasting content to the reception side without using thebroadcasting band of digital television broadcasting is considered, inwhich the reception side is controlled by the broadcasting side todownload data broadcasting content from a predetermined server via theInternet.

However, if this method is implemented, the accesses from the receptionside to a predetermined server would temporally concentrate to cause anInternet congestion and the increase in server processing load, therebypresenting a problem that data broadcasting content cannot be quicklydownloaded, for example. To overcome this problem, some measures must betaken to avoid temporal access concentration from the reception side toa predetermined server. However, such measures have not been establishedup until the present point of time.

Therefore, the present invention addresses the above-identified andother problems associated with related-art methods and apparatuses andsolves the addressed problems by providing a transmission apparatus, atransmission method, a reception apparatus, a reception method, aprogram, and a broadcasting system that are configured to control thereception side from the broadcasting side such that the accesses fromthe reception side to a predetermined server are temporally distributed.

In carrying out the invention and according to a first embodimentthereof, there is provided a transmission apparatus for transmitting AV(AudioNideo) content. This transmission apparatus includes: acquisitionmeans for acquiring an estimated number of audience terminals indicativeof an estimated number of reception apparatuses receiving the AVcontent; computation means for, in conjugation with the AV content,computing, on the basis of the estimated number of audience terminals, avalidity probability of trigger information associated with control ofan application program to be executed in the reception apparatus;generation means for generating the trigger signal including thecomputed validity probability; and transmission means for transmittingthe generated trigger information with the AV content.

In the above-mentioned transmission apparatus, the generation meansgenerates, including the computed validity probability, triggerinformation for controlling, in the reception apparatus, at least one ofprocessing of acquiring the application program, processing of launchingthe acquired application program, processing of event firing in theactive application program, processing of suspending the activeapplication program, and processing of terminating the activeapplication program.

In the above-mentioned transmission apparatus, the generation meansgenerates, including the computed validity probability, the triggerinformation for controlling, in the reception apparatus, at least one ofprocessing of acquiring the application program that involves processingof accessing a predetermined server and processing of event firing inthe active application program.

In the above-mentioned transmission apparatus, the acquisition meansacquires the estimated number of audience terminals on the basis of pastviewing statistics.

In the above-mentioned transmission apparatus, the acquisition meansacquires the estimated number of audience terminals on the basis ofactual measurements of access to the server.

In carrying out the invention and according to the first embodimentthereof, there is provided a transmission method for a transmissionapparatus for transmitting AV (AudioNideo) content. This transmissionmethod includes the steps of: acquiring, by the transmission apparatus,an estimated number of audience terminals indicative of an estimatednumber of reception apparatuses receiving the AV content; computing, bythe transmission apparatus, in conjugation with the AV content, on thebasis of the estimated number of audience terminals, a validityprobability of trigger information associated with control of anapplication program to be executed in the reception apparatus;generating, by the transmission apparatus, the trigger informationincluding the computed validity probability; and transmitting, by thetransmission apparatus, the generated trigger information with the AVcontent.

In carrying out the invention and according to the first embodimentthereof, there is provided a program for controlling a transmissionapparatus for transmitting AV (AudioNideo) content. This program causesa computer of the transmission apparatus to execute processing includingthe steps of: acquiring an estimated number of audience terminalsindicative of an estimated number of reception apparatuses receiving theAV content; computing, in conjugation with the AV content, on the basisof the estimated number of audience terminals, a validity probability oftrigger information associated with control of an application program tobe executed in the reception apparatus; generating the triggerinformation including the computed validity probability; andtransmitting the generated trigger information with the AV content.

In the first embodiment of the invention, the estimated number ofaudience terminals indicative of the estimated number of receivingapparatuses receiving AV content is acquired. In conjugation with thereceived AV content, the validity probability of the trigger informationassociated with the control of an application program to be executed onthe reception apparatus is computed on the basis of the estimated numberof audience terminals. Trigger information is generated including thecomputed validity probability. The generated trigger information istransmitted with AV content.

In carrying out the invention and according to a second embodimentthereof, there is provided a reception apparatus for receivingtransmitted AV (AudioNideo) content. This reception apparatus includes:extraction means for extracting trigger information associated withcontrol of an application program, transmitted with the AV content, tobe executed in conjugation with the AV content; determination means fordetermining whether the trigger information is valid on the basis of avalidity probability included in the extracted trigger information; andcontrol means for controlling processing associated with the applicationprogram in response to a command indicated by the extracted triggerinformation only when the trigger information is determined to be valid.

In the above-mentioned reception apparatus, the control means controlsat least one of processing of acquiring the application program,processing of launching the acquired application program, processing ofevent firing in the active application program, processing of suspendingthe active application program, and processing of terminating the activeapplication program in accordance with a command indicated by theextracted trigger information only when the trigger information isdetermined to be valid.

In the above-mentioned reception apparatus, the control means controlsat least one of processing of acquiring the application program thatinvolves processing of accessing a predetermined server and processingof event firing in the active application program in accordance with acommand indicated by the extracted trigger information only when thetrigger information is determined to be valid.

In carrying out the invention and according to the second embodimentthereof, there is provided a reception method for a reception apparatusfor receiving transmitted AV (Audio/Video) content. This receptionmethod includes the steps of: extracting, by the reception apparatus,trigger information associated with control of an application program,transmitted with the AV content, to be executed in conjugation with theAV content; determining, by the reception apparatus, whether the triggerinformation is valid on the basis of a validity probability included inthe extracted trigger information; and controlling, by the receptionapparatus, processing associated with the application program inresponse to a command indicated by the extracted trigger informationonly when the trigger information is determined to be valid.

In carrying out the invention and according to the second embodimentthereof, there is provided a program for controlling a receptionapparatus for receiving transmitted

AV (AudioNideo) content. This program causes a computer of the receptionapparatus to execute processing including the steps of: extractingtrigger information associated with control of an application program,transmitted with the AV content, to be executed in conjugation with theAV content; determining whether the trigger information is valid on thebasis of a validity probability included in the extracted triggerinformation; and controlling processing associated with the applicationprogram in response to a command indicated by the extracted triggerinformation only when the trigger information is determined to be valid.

In the second embodiment of the invention, the trigger informationassociated with the control of an application program to be executed inconjugation with AV content, this application program being transmittedwith the AV content, is extracted. The extracted trigger information isdetermined whether valid or not on the basis of the validity probabilityincluded in this extracted trigger information. Only when the triggerinformation is determined to be valid, the processing associated withthe application program is controlled in accordance with a commandindicated by the extracted trigger information.

In carrying out the invention and according to a third embodimentthereof, there is provided a broadcasting system including: atransmission apparatus for transmitting AV (Audio/Video) content; and areception apparatus for receiving the AV content transmitted from thetransmission apparatus. In this broadcasting system, the transmissionapparatus has acquisition means for acquiring an estimated number ofaudience terminals indicative of an estimated number of receptionapparatuses receiving the AV content, computation means for, inconjugation with the AV content, computing, on the basis of theestimated number of audience terminals, a validity probability oftrigger information associated with control of an application program tobe executed in the reception apparatus, generation means for generatingthe trigger information including the computed validity probability, andtransmission means for transmitting the generated trigger informationwith the AV content. In this broadcasting system, the receptionapparatus has extraction means for extracting trigger informationtransmitted with the AV content, to be executed in conjugation with theAV content, determination means for determining whether the triggerinformation is valid on the basis of a validity probability included inthe extracted trigger information, and control means for controllingprocessing associated with the application program in response to acommand indicated by the extracted trigger information only when thetrigger information is determined to be valid.

In the third embodiment of the invention, the following processing isexecuted by the transmission apparatus. The estimated number of audienceterminals indicative of the estimated number of reception apparatusesreceiving AV content is acquired. In conjugation with AV content, avalidity probability of the trigger information associated with thecontrol of an application program to be executed on the receptionapparatus is computed on the basis of the estimated number of audienceterminals. The trigger information is generated by including thecomputed validity probability. The generated trigger information istransmitted with AV content. The following processing is executed by thereception apparatus. The trigger information associated with the controlof an application program to be executed in conjugation with AV contentis extracted, this application being transmitted with the AV content.The trigger information is determined whether valid or not on the basisof the validity probability included in the extracted triggerinformation. Only when the trigger information is determined to bevalid, the processing associated with the application program iscontrolled in accordance with a command indicated by the extractedtrigger information.

According to the first embodiment of the invention, control is providedsuch that many reception apparatuses access a predetermined server in atemporally distributed manner.

According to the second embodiment of the invention, the processing ofaccessing a predetermined server is executed under the control of atransmission apparatus.

According to the third embodiment of the invention, the accesses to apredetermined server from reception apparatuses are temporallydistributed.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features of the invention will become apparent from the followingdescription of embodiments with reference to the accompanying drawingsin which:

FIGS. 1A and 1B are diagrams illustrating a broadcasting band fordigital television broadcasting;

FIG. 2 is a schematic block diagram illustrating an exemplaryconfiguration of a broadcasting system practiced as one embodiment ofthe present invention;

FIG. 3 is a block diagram illustrating an exemplary configuration of areception apparatus practiced as another embodiment of the presentinvention;

FIG. 4 is a diagram illustrating a concept of transmitting triggerinformation as stored in a PCR packet of a TS;

FIG. 5 is a diagram illustrating a specific arrangement of a triggerinformation in the PCR packet;

FIGS. 6A and 6B are diagrams illustrating examples of embedding atrigger information in a video signal;

FIG. 7 is a diagram illustrating items in the trigger information of aprecache command;

FIG. 8 is a diagram illustrating items in the trigger information of anexecute command;

FIG. 9 is a diagram illustrating items in the trigger information of aninject event command;

FIG. 10 is a diagram illustrating items included in the triggerinformation of a suspend command;

FIG. 11 is a diagram illustrating items included in the triggerinformation of a terminate command;

FIG. 12 is a diagram illustrating one example of a syntax of triggerinformation;

FIGS. 13A, 13B, 13C, 13D, 13E, 13F, and 13G are diagrams illustratingdisplay examples to be obtained when a data broadcasting applicationprogram is executed in conjugation with the progress of programs andCMs;

FIG. 14 is a flowchart indicative of trigger information respondingprocessing;

FIGS. 15A and 15B are diagrams illustrating the effects ofTrigger_validity;

FIGS. 16A and 16B are diagrams illustrating the effects ofTrigger_validity;

FIG. 17 is a diagram illustrating an exemplary operation scenario of anapplication program;

FIG. 18 is a schematic diagram illustrating status transitions of anapplication program of the reception apparatus;

FIG. 19 is a diagram illustrating a first operation scenario;

FIG. 20 is a diagram illustrating a second operation scenario;

FIG. 21 is a diagram illustrating a third operation scenario;

FIG. 22 is a diagram illustrating a fourth operation scenario;

FIG. 23 is a diagram illustrating a fifth operation scenario; and

FIG. 24 is a block diagram illustrating an exemplary configuration of acomputer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention will be described in further detail by way of embodimentsthereof with reference to the accompanying drawings.

[Exemplary Configuration of a Broadcasting System]

Now, referring to FIG. 2, there is shown a schematic block diagramillustrating a broadcasting system practiced as one embodiment of theinvention. This broadcasting system 30 is made up of a broadcastingapparatus 41 and a server 46 that are arranged at the broadcastingstation side and a reception apparatus 60 that is arranged at eachreception side.

With the broadcasting system 30, each reception apparatus 60 accessesthe server 46 in accordance with trigger information that is transmittedas included in a digital television broadcast signal. To be morespecific, whether or not each reception apparatus 60 executes access onthe basis of validity probability parameter N written to itemTrigger_validity of trigger information is determined, therebydistributing the access from each reception apparatus 60 during a periodin which the trigger information is transmitted two or more times.

It should be noted that the reception apparatus 60 accesses the server46 to download therefrom data broadcasting content to be executed inconjugation with the AV content of a program and a CM and uploadpredetermined information to the server 46 by being fired as an event ofthe active data broadcasting content, for example.

Data broadcasting content is realized when an application programsupplied to a reception apparatus is executed by the computer of thereception apparatus, so that the data broadcasting content is hereafterreferred to also as a data broadcasting application program or a databroadcasting application.

The broadcasting apparatus 41 transmits digital television broadcastsignals. At the same time, the broadcasting apparatus 41 transmits, asincluded in a digital television broadcast signal, trigger informationthat is a command for controlling the execution of data broadcastingcontent to be executed in conjugation with the progress of a program ora CM.

The broadcasting apparatus 41 has an access count measuring block 42, avalidity probability computation block 43, a trigger informationgeneration block 44, and a transmission block 45.

The access count measuring block 42 measures the number of accesses madefrom the reception apparatus 60 to the server 46. The validityprobability computation block 43 computes validity probability parameterN that is one of the items of trigger information. The computation ofvalidity probability parameter N is made on the basis of the number ofmeasured accesses made to the server 46, an obtained estimated totalnumber of reception apparatuses 60, an estimated audience ratio of abroadcast program, an estimated number of running reception apparatuses60, and a period in which the same trigger information is repeatedlytransmitted.

The trigger information generation block 44 generates triggerinformation for controlling the execution of a data broadcastingapplication in the reception apparatus 60. With the generated triggerinformation, validity probability parameter N computed by the validityprobability computation block 43 is written to item Trigger_validity. Itshould be noted that there may be trigger information that has no itemTrigger_validity.

Trigger information includes the information indicative of command typeand the information for identifying corresponding data broadcastingcontent, in addition to validity probability parameter N describedabove. Details of the trigger information will be described later.

The transmission block 45 transmits the generated trigger information asmultiplexed with a transport stream (TS) of digital television broadcastsignals or embedded in a video signal.

In response to a request from the reception apparatus 60 that hasaccessed the server 46 via the Internet 50, the server 46 supplies adata broadcasting application to the reception apparatus 60 (namely,makes the reception apparatus 60 download the data broadcastingapplication). In addition, the server 46 receives an access(questionnaire replies for example) from the reception apparatus 60 byan event (a questionnaire during a program for example) fired in theactive data broadcasting application.

The reception apparatus 60 receives a digital broadcasting signalbroadcast from the broadcasting apparatus 41 and outputs the video andaudio of AV content (a television program, a CM, and so on) to a displaymonitor at subsequent stage, not shown. In addition, the receptionapparatus 60 accesses the server 46 via the Internet 50 to obtain a databroadcasting content. In addition, by executing the data broadcastingcontent in accordance with the received trigger information, thereception apparatus 60 presents various kinds of information to the userin conjugation with the progress of a program and accesses the server46.

It should be noted that this reception apparatus 60 may be arranged as astandalone unit or as incorporated in a television receiver or a videorecorder, for example.

[Exemplary Configuration of the Reception Apparatus]

Referring to FIG. 3, there is shown an exemplary configuration of thereception apparatus 60. The reception apparatus 60 is made up of a tuner61, a demultiplexer 62, an audio decoder 63, an audio output block 64, avideo decoder 65, a trigger detection block 66, a video output block 67,a control block 68, a memory 69, an operator block 70, a recording block71, a communication I/F 72, a cache memory 73, an application engine 74,and an application memory 75.

The tuner 61 receives a digital television broadcasting signalcorresponding to a channel selected by a user, demodulates the receivedsignal, and outputs a resultant TS to the demultiplexer 62. Thedemultiplexer 62 separates the TS supplied from the tuner 61 into anaudio encoded signal, a video encoded signal, and a control signal andsupplies these signals to the audio decoder 63, the video decoder 65,and the control block 68, respectively.

Further, the demultiplexer 62 extracts a PCR (Program Clock Reference)packet stored in the trigger information from the TS and outputs theextracted PCR packet to the trigger detection block 66.

The audio decoder 63 decodes the entered audio encoded signal andoutputs a resultant audio signal to the audio output block 64. The audiooutput block 64 outputs the entered audio signal to a subsequent stage(a loudspeaker for example).

The video decoder 65 decodes the entered video encoded signal andoutputs a resultant video signal to the trigger detection block 66 andthe video output block 67.

The trigger detection block 66 always monitors the entered video signalto detect trigger information embedded in the video signal and outputsthe detected trigger information to the control block 68 (if the triggerinformation is arranged only in a PCR packet of a TS, the operation ofthis trigger detection block 66 is not required). In addition, thetrigger detection block 66 extracts trigger information from a PCRpacket entered from the demultiplexer 62 and outputs the extractedtrigger information to the control block 68.

The video output block 67 outputs the video signal entered from thevideo decoder 65 to a subsequent stage. In addition, the video outputblock 67 combines the video signal of the data broadcasting contententered from the application engine 74 and the video signal entered fromthe video decoder 65 and outputs a resultant signal to a subsequentstage.

The control block 68 controls the entire reception apparatus 60 byexecuting a control program stored in the memory 69. Also, on the basisof the trigger information entered from the trigger detection block 66,the control block 68 controls the acquisition, launching, event-firing,pausing, and terminating of the data broadcasting application.

The memory 69 stores the control program that is executed by the controlblock 68. This control program can be updated on the basis of the updatedata that is obtained from a digital television broadcasting signal orvia the Internet 50. The operator block 70 receives operations done bythe user and supplies the operation signals corresponding to theoperations to the control block 68.

The memory 69 also stores such user profile information entered by theuser in advance as user's age, gender, address, and so on.

This profile information is referenced by the active data broadcastingapplication for example and, only if the user profile informationsatisfies a predetermined condition, can be used for event firing forexample. Also, this profile information may be uploaded to the server46.

If a data broadcasting application is distributed by use of a digitaltelevision broadcast signal, the recording block 71 stores a downloadeddata broadcasting application in the recording media incorporated in therecording block 71.

The communication I/F 72 connects the reception apparatus 60 to theserver 46 via the Internet 50 under the control of the applicationengine 74. Under the control of the control block 68, the applicationengine 74 obtains a data broadcasting application from the server 46 viathe communication I/F 72 and the Internet 50 and stores the databroadcasting application in the cache memory 73.

Under the control of the control block 68, the application engine 74reads the data broadcasting application from the recording block 71 orthe cache memory 73 to execute the data broadcasting application.

The application memory 75 is composed of a work memory 75A and a savememory 75B. The application engine 74 stores data (to be more specific,the data including the layer of displayed information) associated withthe active data broadcasting application into the work memory 75A. Ifthe application engine 74 suspends the active data broadcastingapplication, the application engine 74 moves the data in the work memory75A of the application memory 75 to the save memory 75B. To restart thesuspended data broadcasting application, the application engine 74 movesthe data from the save memory 75B to the work memory 75A to resume thestate as it was before the pausing.

It should be noted that the two areas of the same size in theapplication memory 75 may be alternately specified as the work memory75A and the save memory 75B. This memory switching arrangementeliminates the necessity of moving data between the work memory 75A andthe save memory 75B.

[Trigger Information Transmission Method]

The following describes a method of transmitting trigger information.

As described above, trigger information can be arranged in a PCR packetof a TS of a digital television broadcast signal, embedded in a videosignal, or arranged in the user data area of an MPEG2 (Moving PictureExperts Group phase 2) video stream multiplexed with the TS.

Referring to FIG. 4, there is shown a concept in which triggerinformation is arranged in a PCR packet of the TS of a digitaltelevision broadcast signal.

As shown in the figure, trigger information is not stored in all PCRpackets, but stored in a PCR packet only with a timing proper forlinking to a program or a CM.

It should be noted that trigger information is transmitted two or moretimes consecutively in the same contents (namely, the same command forthe same data broadcasting application, for example) in consideration ofan electromagnetic interference or a failure (or a reception failure) ofthe reception apparatus 60. However, the trigger information having thesame contents to be transmitted two or more times does not have the samevalidity probability parameter N written to item Trigger_validity.

Referring to FIG. 5, there is shown a location at which triggerinformation is stored in a PCR packet. With a PCR packet, PCR is storedin adaptation_field of a TS packet, in which trigger information(Trigger_Info_descriptor) is stored in transport_private_data_bytesubsequent to PCR. It should be noted that, if trigger information isstored, transport_private_data_flag of Various_flags arranged in frontof PCR is set to “1.”

Referring to FIGS. 6A and 6B, there are shown two types of examples ofembedding trigger information in a video signal.

FIG. 6A shows an example in which trigger information istwo-dimensionally barcoded to be superimposed on a predeterminedlocation (the lower right corner in this case) of the image of a videosignal. FIG. 6B shows an example in which trigger information isvideo-coded to be superimposed on the lower several lines of the imageof a video signal. The trigger information shown in FIG. 6A and FIG. 6Bis detected by the trigger detection block 66 of the reception apparatus60.

In each of FIG. 6A and FIG. 6B, trigger information is arranged on thescreen of a television program, so that, in the case where a televisionprogram is redistributed by use of a CATV network for example, thetelevision program can also be transmitted to the reception apparatus 60with the trigger information undeleted.

In each of the examples shown in FIG. 6A and FIG. 6B, the triggerinformation (a two-dimensional barcode or a video code) on the screen isvisually recognizable by the user of the reception apparatus 60;however, if this is not desired, the two-dimensional barcode or thevideo code may be masked by the pixels therearound before beingdisplayed.

In the example described above, trigger information is transmitted asstored in a PCR. However, the storage location and the transmissionmethod of trigger information are not restricted to those of thisexample.

[Detail of Trigger Information]

The following describes details of trigger information. Triggerinformation is classified into five types according to commandsindicated by the trigger information. There are five types of commands;pre-cache command, execute command, inject event command, suspendcommand, and terminate command. It is also practicable to add othercommands to the above-mentioned commands.

Referring to FIG. 7, there are shown items included in triggerinformation that is a pre-cache command. A pre-cache command specifiesthe reception apparatus 60 to acquire a data broadcasting application.

In the pre-cache command, Trigger_id is information for identifying thistrigger information. If pieces of trigger information having the samecontents are transmitted two or more times, each piece of triggerinformation has the same Trigger_id. Protocol_version is indicative ofthe version of a protocol of this trigger information. Command_code isindicative of the type of the command of this trigger information. Inthe example shown in FIG. 7, Command_code has information indicative ofa pre-cache command.

Trigger_validity is written with validity probability parameter Nindicative of a value for specifying a probability when each receptionapparatus 60 that has received this trigger information is determined toexecute processing in accordance with this trigger information in orderto distribute the accesses to the server 46 from the receptionapparatuses 60.

For example, in order to distribute the access to the server 46 by manyreception apparatuses 60 into four groups, the same trigger informationmay be transmitted four times: namely, in the first trigger information,validity probability parameter N=4; in the second trigger information,validity probability parameter N=3; in the third trigger information,validity probability parameter N=2; and in the fourth triggerinformation, validity probability parameter N=1.

Notifying the reception apparatuses 60 of the validity probability canprevent the temporary concentration of the processing for a databroadcasting application by the accesses from two or more receptionapparatuses 60 to the server 46.

It should be noted that, in the trigger information (for example, thetrigger information of a suspend command or a terminate command to bedescribed later) for controlling the processing of not accessing theserver 46 for example, the validity probability may always be set to 1.

The access distribution by use of Trigger_validity will be describedlater with reference to FIGS. 15A and 15B, FIGS. 16A and 16B, FIG. 19and subsequent figures.

App_id is information for identifying a data broadcasting application tobe obtained in correspondence with this trigger information. App_type isinformation indicative of the type (HTML5, BML, Java or the like forexample) of the data broadcasting application corresponding to thistrigger information. App_url is the URL of the acquisition source (theserver 46 in this case) of the data broadcasting application.

Broadcast_App_flag, Downloaded_App_flag, and Internet_App_flag areindicative of locations of the program data of the data broadcastingapplications corresponding to this trigger information.Broadcast_App_flag is set to “1” if the data broadcasting applicationcorresponding to this trigger information is obtainable from a digitaltelevision broadcast signal. Downloaded_App_flag is set to “1” if thedata broadcasting application corresponding to this trigger informationhas already been broadcast by a downloaded broadcast service andtherefore is obtainable from a local storage (the recording block 71 forexample) if the data broadcasting application has been received by thereception apparatus 60. Internet_App_flag is set to “1” if the databroadcasting application corresponding to this trigger information isobtainable from the application server 46 via the Internet 50.

Referring to FIG. 8, there are shown items included in triggerinformation that is an execute command. An execute command specifies thereception apparatus 60 to launch a data broadcasting application.

Trigger _id, Protocol_version, Command_code, Trigger_validity, App_id,App_type, App_url, Broadcast_App_flag, Downloaded_App_flag, andInternet_App_flag are substantially the same as those of the triggerinformation that is a pre-cache command shown in FIG. 7. A difference,however, lies in that Command_code has information indicative of anexecute command.

App_life_scope is indicative whether or not to terminate the active databroadcasting application in response to the switching of video.App_expire_date is indicative of a date on which to terminate the activedata broadcasting application without receiving a terminate command.

Referring to FIG. 9, there are shown items included in triggerinformation that is an inject event command. An inject event commandcauses the reception apparatus 60 to fire an event in the active databroadcasting application.

An event herein denotes a timing with which to start the processing ofswitching the information displayed by a data broadcasting application,the processing of uploading (or notifying) audience questionnaireresults executed in a program to the server 46, and so on, for example.

Trigger_(——)id, Protocol_version, Command_code, Trigger_validity,App_id, and App_type are substantially the same those of the triggerinformation that is a pre-cache command shown in FIG. 7. A difference,however, lies in that Command_code has information indicative of aninject event command.

Writing proper validity probability parameter N to Trigger_validity thatis the trigger information as an inject event command can distribute theevent occurrence timings in the two or more reception apparatuses 60that are receiving a program. This prevents the temporary concentrationof the accesses from two or more reception apparatuses 60 to the server46, thereby dispersing the accesses.

Event_id is identification information about an even to be fired in thedata broadcasting application specified by App_id. Event embedded datahas data that is referenced when firing the event.

Referring to FIG. 10, there are shown items included in triggerinformation that is a suspend command. A suspend command causes thereception apparatus 60 to suspend the active data broadcastingapplication.

Trigger_(——)id, Protocol_version, Command_code, Trigger_validity,App_id, and App_type are substantially the same as those of the triggerinformation that is a pre-cache command shown in FIG. 7. A difference,however, lies in that Command_code has information indicative of asuspend command.

Referring to FIG. 11, there are shown items included in triggerinformation that is a terminate command. A terminate command causes thereception apparatus 60 to terminate the active data broadcastingapplication.

Trigger_id, Protocol_version, Command_code, Trigger_validity, App_id,and App_type are substantially the same as those of the triggerinformation that is a pre-cache command shown in FIG. 7. A difference,however, lies in that Command_code has information indicative of aterminate command.

[Syntax of Trigger Information]

Referring to FIG. 12, there is shown an example of a syntax of triggerinformation compliant with the trigger information that is each of thecommands described above. It should be noted that the syntax of triggerinformation is not restricted to that shown in FIG. 12. Any othersyntaxes are available.

[Explanation of Operations]

The following describes an overview of operations to be executed by thereception apparatus 60 in response to received trigger information,especially the transitions of the screen display.

Referring to FIGS. 13A to 13G, there are shown transitions between thedisplay screens of the reception apparatus 60 when the data broadcastingapplication corresponding to a television program or a CM is executed bythe reception apparatus 60.

For example, as shown in FIG. 13A, when a television program (in thisexample, “News of 7:00”) is being broadcast and the contents of theprogram transition to economic information, the trigger information ofan execute command for launching the data broadcasting applicationcorresponding to the program is transmitted. When this triggerinformation is received, the data broadcasting application is launchedand, on the screen on which the program is displayed, an icon (in thisexample, “Stock”) for prompting the user to display the databroadcasting application is displayed as shown in FIG. 13B.

When the user clicks this icon, the display (in this example, stockprice information display) by the data broadcasting application isexecuted as shown in FIG. 13C. Thus, only when the icon for promptingthe user to display the data broadcasting application is displayed, thedisplay by the data broadcasting application is executed, therebypreventing the trouble for the user who does not require the display bythe data broadcasting application. It should be noted however that theabove-mentioned icon display is also the first display of the databroadcasting application.

When the contents of the program further transition (to the sportinformation in this example), the trigger information of an inject eventcommand for firing the event is transmitted in response. When the injectevent command is received, an event is fired, thereby changing thedisplay by the data broadcasting application on the screen as shown inFIG. 13D (in this example, to game results information display).

Next, a suspend command for suspending the active data broadcastingapplication corresponding to the program is transmitted. When thissuspend command is received, the active data broadcasting application issuspended. Then, the trigger information of an execute command forlaunching the data broadcasting application corresponding to the CM istransmitted. When this execute command is received, the databroadcasting application for the CM program is launched. Consequently,on the screen on which the CM is displayed, an icon (“Prize Application”in this example) for prompting the user to display the data broadcastingapplication corresponding to the CM is displayed as shown in FIG. 13E.

When the user clicks this icon, the display (in this example, thedisplay for prize application) is executed on the screen by the databroadcasting application corresponding to the CM.

When the display of the CM has been completed, in conjunction withresuming of the program, the trigger information of an execute commandfor resuming the data broadcasting application corresponding to theprogram is transmitted. When this execute command is received, the databroadcasting application for the CM is terminated and the display ofthis data broadcasting application is deleted, upon which the databroadcasting application of the program is resumed from the suspendedstate as shown in FIG. 13F.

Then, when the program ends, the trigger information of a terminatecommand for terminating the data broadcasting application correspondingto the program is transmitted. When this trigger information isreceived, the display of the data broadcasting application is deletedfrom the screen as shown in FIG. 13G and only the video of the programis displayed.

It should be noted that a data broadcasting application can be displayednot only by a method in which the display area of a program is shrunk toprovide the area for displaying the data broadcasting application asshown in FIGS. 13A to 13G, but also by another method in which thedisplay of a data broadcasting application is superimposed on thedisplay of a program, for example.

The following describes an operation (hereafter referred to triggerinformation handling processing) to be executed upon reception oftrigger information by the reception apparatus 60.

Referring to FIG. 14, there is shown a flowchart indicative of thetrigger information handling processing. This trigger informationhandling processing is repeatedly executed while the user is viewing atelevision program, namely, while the reception apparatus 60 isreceiving digital television broadcast signals.

In step S1, the trigger detection block 66 waits until a PCR packetincluding trigger information is entered from the demultiplexer 62 ortrigger information is detected from a video signal outputted from thevideo decoder 65. When a PCR packet including trigger information isentered or trigger information is detected from a video signal, theprocedure goes to step S2.

In step S2, the trigger detection block 66 outputs trigger informationto the control block 68. The control block 68 reads Trigger_id of thereceived trigger information to determine whether the processing of stepS4 and subsequent steps has already been executed on this triggerinformation. If the processing of step S4 and subsequent steps is foundexecuted on this trigger information, then the procedure is returned tostep S1 to repeat the above-mentioned processing therefrom. By contrast,if the processing of step S4 and subsequent steps is found not executedon this trigger information, then the procedure goes to step S3.

In step S3, the control block 68 determines on the basis of validityprobability parameter N written to Trigger_validity in the triggerinformation whether the processing of this time is valid or not (whetherto advance the procedure to step S4 and later or to return to step S11).It should be noted that, if Trigger_validity is not arranged in thetrigger information (or if validity probability parameter N=1), theprocedure goes to step S4.

The following describes the decision of whether the processing of thistime is valid or not.

Referring to FIGS. 15A and 15B, there are shown a comparison in the casewhere Trigger_validity is not arranged (or validity probabilityparameter=1) and a comparison in the case where Trigger_validity isarranged. If Trigger_validity is not arranged, although the same triggerinformation is transmitted two or more times, most reception apparatuses60 respond to the first trigger information, resulting in theconcentration of accesses to the server 46 and so on as shown in FIG.15A.

By contrast, if Trigger_validity is arranged and the validityprobability is set to a proper value, the active reception apparatuses60 can be allocated to the same trigger information in a distributedmanner that is transmitted two or more times, thereby preventing theconcentration of accesses to the server 46 and so on as shown in FIG.15B.

For example, as shown in FIG. 16B, if the broadcasting station intendsto distribute the accesses from any active reception apparatuses 60 tothe server 46 and so on into four times, the broadcasting apparatus 41transmits the same trigger information four times, in which validityprobability parameter N=4 for the Trigger_validity in the first triggerinformation, validity probability parameter N=3 in the second triggerinformation, validity probability parameter N=2 in the third triggerinformation, and validity probability parameter N=1 in the fourthtrigger information.

In response, the control block 68 of the reception apparatus 60determines validity or invalidity in accordance with random numbersunder the condition of validity probability.

Consequently, if it is supposed that 100000 units, for example, ofreception apparatuses 60 be executing, at the same time, the processingfor trigger information, then validity is determined on about 25000units (=100000/4) of the reception apparatuses 60 by the first triggerinformation (validity probability 1/N=1/4), validity is determined onabout another 25000 units (=75000/3) of the reception apparatuses 60 bythe second trigger information (validity probability=1/3), validity isdetermined on about still another 25000 units (=50000/2) of thereception apparatuses 60 by the third trigger information (validityprobability=1/2), and validity is determined on all remaining units(=25000/1) of the reception apparatuses 60 by the fourth triggerinformation (validity probability=1/1).

Referring to FIG. 14 again, the control block 68 reads Command_code oftrigger information in step S4 to determine whether the commandindicated by this trigger information is a pre-cache command, an executecommand, an inject event command, a suspend command, or a terminatecommand.

In step S5, the control block 68 determines whether the decision resultin step S4 is a pre-cache command. If the decision result is found to bea pre-cache command, then the procedure goes to step S6.

In step S6, the program data of the data broadcasting applicationidentified by App_id of this trigger information is obtained.

To be more specific, if Broadcast_App_flag of this trigger informationis “1,” then the program data of the data broadcasting identified byApp_id is obtained from the television broadcasting signal to berecorded to the recording block 71. If Downloaded_App_flag of thistrigger information is “1,” then the program data of the databroadcasting application identified by App_id is obtained from therecording block 71 that is a local storage. If Internet_App_flag of thistrigger information is “1,” then the program data of the databroadcasting application identified by App_id is obtained from theserver 46 via the Internet 50 to be recorded to the cache memory 73.

It should be noted that if two or more of Broadcast_App_flag,Downloaded_App_flag, and Internet_App_flag are “1,” then, in accordancewith the condition of the reception apparatus 60, the program data ofthe data broadcasting application identified by App_id of this triggerinformation can be obtained. Subsequently, the procedure is returned tostep S1 to repeat the above-mentioned processing therefrom.

In step S5, if the decision result in step S4 is found not to be apre-cache command, then the procedure goes to step S7. In step S7, thecontrol block 68 determines whether the decision result in step S4 is anexecute command. If the decision result is found to be an executecommand, then the procedure goes to step S8.

In step S8, under the control of the control block 68, the applicationengine 74 determines whether the data broadcasting applicationidentified by App_id of this trigger is suspended. To be more specific,the application engine 74 determines that the data broadcastingapplication is suspended if the data indicative of suspension of thedata broadcasting application identified by App_id is saved to the savememory 75B.

In step S8, if the data broadcasting application identified by App_id isfound not suspended, then the procedure goes to step S9. In step S9,under the control of the control block 68, the application engine 74obtains the program data of the data broadcasting application identifiedby App_id if this program data has not been obtained (that is, thisprogram data is not found in the recording block 71 or the cache memory73).

In step S10, under the control of the control block 68, the applicationengine 74 terminates the active data broadcasting application if any.

In step S11, under the control of the control block 68, the applicationengine 74 launches the data broadcasting application identified byApp_id. Then, the procedure is returned to step S1 to repeat theabove-mentioned processing therefrom.

It should be noted that, if the data broadcasting application identifiedby App_id is found suspended in step S8, then the procedure goes to stepS12. In step S12, under the control of the control block 68, theapplication engine 74 moves the data from the save memory 75B to thework memory 75A and launches the data broadcasting applicationidentified by App_id. Consequently, the suspended data broadcastingapplication identified by App_id is resumed from the suspended state.Then, the procedure is returned to step S1 to repeat the above-mentionedprocessing therefrom.

In step S7, if the decision result in step S4 is found not to be anexecute command, then the procedure goes to step S13. In step S13, thecontrol block 68 determines whether the decision result in step S4 is aninject event command. If the decision result is found to be an injectevent command, then the procedure goes to step S14.

In step S14, the control block 68 controls the application engine 74only when App_id of this trigger information matches App_id of theactive data broadcasting application, thereby firing (executing) theevent corresponding to Event_id of trigger information in the activeapplication. Next, the procedure is returned to step S1 to repeat theabove-mentioned processing therefrom.

In step S13, if the decision result in step S4 is found not to be aninject event command, then the procedure goes to step S15. In step S15,the control block 68 determines whether the decision result in step S4is a suspend command. If the decision result is found to be a suspendcommand, then the procedure goes to step S16.

In step S16, under the control of the control block 68, the applicationengine 74 saves the data (namely, the data currently stored in the workmemory 75A; if the information to be displayed has a layer structure,this data includes the information indicative of the layer of thedisplayed information) indicative of the currently active databroadcasting application to the save memory 75B. Then, the procedure isreturned to step S1 to repeat the above-mentioned processing therefrom.

In step S15, if the decision result in step S4 is found not to be asuspend command, then the decision result in step S4 should have been aterminate command, so that the procedure goes to step S17. In step S17,under the control of the control block 68, the application engine 74terminates the data broadcasting application identified by App_id ifthis data broadcasting application is active. In step S 18, under thecontrol of the control block 68, the application engine 74 deletes thedata associated with the data broadcasting application identified byApp_id from the work memory 75A and the save memory 75B and, at the sametime, deletes the program data of the data broadcasting application fromthe recording block 71 or the cache memory 73. Then, the procedure isreturned to step S1 to repeat the above-mentioned processing therefrom.

Here, the description of the trigger information handling processing hasbeen completed. The above-mentioned trigger information handingprocessing allows the launching of a data broadcasting application, thefiring of an event, and terminating the data broadcasting application inconjugation with a television program or a CM. Further, the triggerinformation handling processing allows the suspension of a databroadcasting application in an active state and the resumption of thesuspended data broadcasting application.

In addition, the above-mentioned trigger information handling processingallows the operation of data broadcasting application as illustratedbelow.

Referring to FIG. 17, there is shown one example of an operationscenario of a data broadcasting application.

When the broadcasting apparatus 41 transmits the trigger information ofa pre-cache command for specifying the acquisition of the program datafor the data broadcasting application corresponding to a program alongthe progress of a television program to the reception apparatus 60, thereception apparatus 60 obtains the specified program data for the databroadcasting application.

Next, when the broadcasting apparatus 41 transmits the triggerinformation of an execute command for the data broadcasting applicationcorresponding to the program to the reception apparatus 60, thereception apparatus 60 launches the data broadcasting application. Uponthis launching, an icon for prompting the user to display the databroadcasting application is displayed on the video of the program in asuperimposed manner.

When the user clicks this icon, the display by the data broadcastingapplication is superimposed on the screen of the video of the program.

When the broadcasting apparatus 41 transmits the trigger information ofan inject event command to the reception apparatus 60 along the progressof the television program, the reception apparatus 60 fires the event inthe active data broadcasting application (for example, the display ischanged).

Then, when the broadcasting apparatus 41 transmits the triggerinformation of a suspend command for the data broadcasting applicationto the reception apparatus 60 with a predetermined timing, the receptionapparatus 60 suspends the active data broadcasting application (theassociated data is held in the save memory 75B). Next, when thebroadcasting apparatus 41 transmits the trigger information of anexecute command for the data broadcasting application to the receptionapparatus 60, the reception apparatus 60 resumes the suspended databroadcasting application.

Further, when the broadcasting apparatus 41 transmits the triggerinformation of a terminate command upon the end of the televisionprogram to the reception apparatus 60, the reception apparatus 60terminates the active data broadcasting application.

[Status Transitions of Data Broadcasting Application]

Now, referring to FIG. 18, there is shown status transitions of a databroadcasting application in the reception apparatus 60.

As shown in FIG. 18, a data broadcasting application transitions to anyone of four types of states; a stopped state, a ready state, an activestate, and a suspended state.

In the stopped state, a data broadcasting application is not executedand the program data of the data broadcasting application has not beenobtained. In the ready state, the program data of the data broadcastingapplication has already been obtained but the data broadcastingapplication is not executed. In the active state, the data broadcastingapplication has been launched and is being executed. In the suspendedstate, the execution of the data broadcasting application isdiscontinued and the information indicative of the discontinued state isheld in the save memory 75B.

If the trigger information of a pre-cache command has been received witha data broadcasting application transitioned to the stopped state andthe program data of the data broadcasting application is obtained, thedata broadcasting application transitions to the ready state.

If the trigger information of an execute command has been received witha data broadcasting application transitioned to the stopped state or theready state and the data broadcasting application is launched, the databroadcasting application transitions to the active state.

If the trigger information of a suspend command has been received with adata broadcasting application transitioned to the active state and theactive data broadcasting application is suspended, the data broadcastingapplication transitions to the suspended state.

If the trigger information of an execute command has been received withthe a data broadcasting application transitioned to the suspended stateand the suspended data broadcasting application is resumed, the databroadcasting application transitions to active state.

If the trigger information of a terminate command has been received witha data broadcasting application transitioned to a ready state, an activestate, or a suspended state, the data broadcasting application in theready state, the active state, or the suspended state transitions to astopped state. It should be noted that the transition to a stopped statemay take place not only on the basis of the trigger information of aterminate command, but also by the reception channel switching that isexecuted upon execution of another data broadcasting application afterpassing of App_expire_date in trigger information.

[Operation Scenario of Access Distribution by use of Trigger_validity]

The following details a method of distributing the accesses from manyactive reception apparatuses 60 to the server 46 by properly settingvalidity probability parameter N to be written to item Trigger_validityin trigger information.

First, the following lists the assumptions for setting proper validityprobability parameter N.

The audience rating of each television program that is executed asrelated with a data broadcasting application can be estimated on thebasis of past statistics (the average audience ratio of similarprograms). Therefore, the total number of reception apparatuses 60(hereafter referred to as estimated number of audience terminals Ne)that are viewing a television program concerned can be estimated.

The minimum period of the transmission frequency (or transmissioninterval) of the trigger information having the same contents (butdifferent valid probabilities) that is transmitted two or more times isassumed to be a length of time necessary for most of the receptionapparatuses 60 that have received the trigger information to determinethat the received trigger information is valid and then access theserver 46. This length of time may be determined to be two seconds forexample on the basis of actually measured and empirical values. In whatfollows, this length of time is referred to as unit time td.

A time range for distributing the accesses to the server 46 (hereafterreferred to as a server access interval) is determined by the purpose ofeach access for each data broadcasting application and defined by twopoints of time, access start point T0 and access expire point Te. Forexample, the server access interval of the trigger information of anexecute command can be defined to be shorter than the server accessinterval of the trigger information of a pre-cache command that istransmitted before the execute command.

The maximum value of the number of accesses per unit time td from thereception apparatus 60 to the server 46 (hereafter referred to as aaccess count target maximum value At) depends on the processingperformance of the server. Therefore, the distribution of the accessesto the server 46 requires an operation in which, on a plane includingthe time axis (or the horizontal axis) and the access count axis (or thevertical axis), a point indicative of an access count of each unit timetd falls in a rectangular area defined by the access distribution timedefined on the time axis and access count target maximum value At on theaccess count axis.

Further, if the point indicative of the access count falls in theabove-mentioned rectangular area, it is required to satisfy a demand forconverging the accesses as early as possible, namely, a demand forshortening the server access interval (policy A) or reducing the accesscount per unit time td as far as possible (policy B).

It is assumed here that the influence due to the congestion of theInternet 50 caused by other than the accesses to the server 46 by thereception apparatus 60 be not put into consideration.

It is also assumed that all the processing performance of the server 46be allocated for the handling of the access from the reception apparatus60, although the server 46 can execute processing other than theprocessing of handling the access from the reception apparatus 60.

It is further assumed that, if the reception apparatuses 60 access theserver 46 with a timing specified by the user, these accesses bedistributed equally in terms of time.

The following operation scenarios 1 through 5 are proposed under theassumptions described above.

[First Operation Scenario]

Now, referring to FIG. 19, there is shown a diagram for describing thefirst operation scenario. The first operation scenario is intended toobtain and launch a new data broadcasting application halfway in programA.

The first operation scenario assumes that almost the total number ofreception apparatuses 60 viewing program A do not change in an accessdistributed time for obtaining a data broadcasting application. In thiscase, the total number Ne of the reception apparatuses 60 viewingprogram A is estimated from the estimated audience rating (based on paststatistics for example) of program A.

Here, let unit time be td, access count target maximum value of theserver 46 be At, and server access interval be (Te−T0), then the numberof trigger information Ntr having the same contents that can betransmitted during a server access interval is equal to (Te−T0)/td.Therefore, the total number of accesses that can be handled by theserver 46 in a server access interval is At·Ntr.

If At·Ntr is less than estimated number of audience terminals Ne(Ne>At·Ntr), then the server access interval must be extended or accesscount target maximum value At must be set higher.

If policy A that converges the access to the server 46 as early aspossible is employed, validity probability parameter N=P1 of itemTrigger_validity in the trigger information to be first transmitted isset to P1=Ne/At (an integer value obtained by rounding up) so that theaccesses from the reception apparatuses 60 equal to the estimated numberof audience terminals Ne are held down to access count target maximumvalue At. Validity probability parameter N=Pk of item Trigger_validityin the trigger information to be transmitted k-th time (k being aninteger of 2 or higher) is set to Pk=(Ne−(k−1)At)/At=P1=(k−1). If Pkgoes equal to or below 1, Pk is set to 1 thereafter.

In order to employ policy B that reduces the number of accesses per unittime td as much as possible, estimated number of audience terminals Neis equally divided by trigger count Ntr=(Te−T0)/Td and validityprobability parameter N of item Trigger_validity in the triggerinformation to be first transmitted is set to P1=Ntr. Validityprobability parameter N=Pk of item Trigger_validity in the triggerinformation to be transmitted k-th time (k being an integer of 2 orhigher) is set to Pk≈Nt−(k−1).

[Second Operation Scenario]

Referring to FIG. 20, there is shown a diagram for describing the secondoperation scenario. The second scenario is intended distribute theaccesses to the server 46 from the last half of program A to the firsthalf of program B by starting the acquisition of a data broadcastingapplication corresponding to program B before the start thereof, namely,during the broadcasting of program A in the same channel, therebylaunching the data broadcasting application upon the start of program B.To be more specific, the trigger information that is a pre-cache commandis transmitted during the broadcasting of program A and the triggerinformation that is an execute command is transmitted at the start ofprogram B. The second operation scenario takes into consideration thatthere are reception apparatuses 60 that do not view program Bcontinuously from program A and there are reception apparatuses 60 thatview program B by selecting this channel from another channel. Namely,the estimation is made by letting the total number of receptionapparatuses 60 viewing program A be estimated number of audienceterminals Nea, the total number of reception apparatuses 60 viewingprogram B be estimated number of audience terminals Neb, and the totalnumber of reception apparatuses 60 that select this channel from anotherchannel to start viewing program B be estimated number of additionalaudience terminals be Ned.

If policy A is employed that shortens, as much as possible, the serveraccess interval (from Ta0 to Tae) in which program A is being broadcast,substantially the same manner as that of the first scenario describedabove is executed. Namely, validity probability parameter N=P1 of itemTrigger_validity in the trigger information that is a pre-cache commandto be first transmitted in program A is set to P1=Nea/At (an integervalue obtained by rounding up) so that the accesses from the receptionapparatuses 60 equal to the estimated number of audience terminals Neare held down to access count target maximum value At. Validityprobability parameter N of item Trigger_validity in the triggerinformation to be transmitted k-th time (k being an integer of 2 orhigher) is set to Pk=(Nea−(k−1)At)/At÷P1−(k−1). If Pk goes equal to orbelow 1, Pk is set to 1 thereafter.

After the start of program B, the accesses by the reception apparatuses60 equal to estimated number of additional audience terminals Ned thatselect this channel from another channel to start viewing program B maybe distributed, so that validity probability parameter N=P1 of itemTrigger_validity in the trigger information that is an execute commandto be first transmitted in program B is set to P1=Ned/At (an integervalue obtained by rounding up). Validity probability parameter N of itemTrigger_validity in the trigger information to be transmitted k-th time(k being an integer of 2 or higher) is set toPk=(Ned−(k−1)At)/At=P1−(k−1). If Pk goes equal to or below 1, Pk is setto 1 thereafter.

[Third Operation Scenario]

Referring to FIG. 21, there is shown a diagram illustrating the thirdoperation scenario. The third scenario is intended to execute, by use ofa data broadcasting application, a voluntary audience voting in apredetermined time zone during which program A is broadcast and collectthe results of the voting by the server 46. To be more specific, by useof a data broadcasting application, a voting button for example isdisplayed in conjugation with the progress of program A and the audienceis made press the displayed button. It should be noted that the votingresults are not supplied to the server 46 immediately after the pressingof the button, but the results are supplied to the server 46 in atemporally distributed manner as an event firing made in response to thetrigger information that is an inject event command.

Therefore, with the third operation scenario, proper validityprobability parameter N may be specified to Trigger_validity in thetrigger information that is an inject event command.

However, because the above-mentioned voting is executed on an audiencevoluntary basis, it is difficult to predict, with a high accuracy,estimated number of audience terminals Nev that is the total number ofreception apparatuses 60 accessing the server 46. So, in the thirdoperation scenario, policy B that reduces the number of accesses perunit time td as much as possible is employed. To be more specific,estimated number of audience terminals Nev is equally divided by thenumber of triggers Ntr=(Te−T0)/Td and validity probability parameter Nof item Trigger_validity in the trigger information that is an injectevent command to be first transmitted is set to P1=Ntr. Validityprobability parameter N of item Trigger_validity in the triggerinformation to be transmitted k-th time (k being an integer of 2 orhigher) is set to Pk Nt−(k−1).

[Fourth Operation Scenario]

Referring to FIG. 22, there is shown a diagram for describing the fourthoperation scenario. The fourth operation scenario is intended, by use ofa data broadcasting application, to cause a predetermined number ofreception apparatuses 60 that are randomly extracted (actually, eachreception apparatus 60 randomly determines on the basis of the validityprobability) from all of the reception apparatuses 60 receiving programA to supply user profile information to the server 46 as a databroadcasting application event.

As described above, letting only a particular ratio of all the receptionapparatuses 60 receiving program A access the server 46 allows theacquisition of such statistical information as audience profile trendswithout imposing much load on the server 46.

To be more specific, above-mentioned estimated number of audienceterminals Ne in the first operation scenario may be replaced by accesstarget count Nep obtained by multiplying estimated number of audienceterminals Ne by a predetermined ratio.

Namely, if policy A for converging the accesses to the server 46 asearly as possible, validity probability parameter N of itemTrigger_validity in the trigger information that is an inject eventcommand to be first transmitted is set to P1=Nep/At (an integer valueobtained by rounding up). Validity probability parameter N of itemTrigger_validity in the trigger information to be transmitted k-th time(k being an integer of 2 or higher) is set toPk=(Nep−(k−1)At/At=P1−(k−1). If Pk goes equal to or below 1, Pk is setto 1 thereafter.

[Fifth Operation Scenario]

Referring to FIG. 23, there is shown a diagram for describing the fifthoperation scenario. In the first scenario through the fourth scenariodescribed above, the total number of reception apparatuses 60 receivinga program is estimated on the basis of past statistics for example. Bycontrast, the fifth operation scenario actually measures the number ofaccesses made from the reception apparatuses 60 that responded to thefirst trigger information to the server 46 and computes the total numberof reception apparatuses 60 on the basis of the obtained actualmeasurements. Therefore, the total number of reception apparatuses 60receiving a program can be grasped comparatively correctly, so thatvalidity probability parameter N of item Trigger_validity in the secondand subsequent trigger information can be set to more proper values.

To be more specific, for the trigger information to be firsttransmitted, validity probability parameter N=P1 is computed on thebasis of estimated number of audience terminals Ne in substantially thesame manner as that of the first operation scenario described above.Then, the number of accesses al from the according reception apparatuses60 is measured to compute the highly accurate estimated number ofreception apparatuses 60 receiving program A as P1·al.

For the trigger information to be transmitted second time and later, theactual number of accesses is subtracted from highly accurate estimatedvalue P1 ·al of the reception apparatuses 60 receiving program A tocompute with high accuracy the number of reception apparatuses 60 notaccessing, thereby computing validity probability parameter N=Pk (kbeing 2 or higher) as shown in the following equation:

Pk=(P1·al−Σai)×c(a(k−1)−At)/At

where, c is a coefficient to be multiplied by a difference from accesscount maximum value At as a feedback element if the number of accessesgoes up or down access count target maximum value At.

As described above, properly setting validity probability parameter N ofitem

Trigger_validity in trigger information allows the temporal distributionof the accesses from the reception apparatus 60 to the server 46.Especially, employment of the fifth operation scenario described aboveallows the more accurate estimation of the total number of receptionapparatuses 60 receiving a program, so that the accesses from thereception apparatus 60 to the server 46 can be distributed moreproperly.

The above-mentioned sequence of processing operations may be executed bysoftware as well as hardware. When the above-mentioned sequence ofprocessing operations is executed by software, the programs constitutingthe software are installed in a computer which is built in dedicatedhardware equipment or installed, from a program recording media, into ageneral-purpose personal computer for example in which various programsmay be installed for the execution of various functions.

Referring to FIG. 24, there is shown a block diagram of an exemplaryhardware configuration of a computer by which the above-mentionedsequence of processing operations are executed.

In this computer 100, a CPU (Central Processing Unit) 101, a ROM (ReadOnly Memory) 102, and a RAM (Random Access Memory) 103 areinterconnected by a bus 104.

The bus 104 is connected to an input/output interface 105. Theinput/output interface 105 is connected to an input block 106 made up ofa keyboard, a mouse, a microphone, and so on, an output block 107 madeup of a display monitor, a loudspeaker, and so on, a storage block 108based on a hard disk unit or a nonvolatile memory, a communication block109 based on a network interface and so on, and a drive 110 configuredto drive a removable media 111 such as a magnetic disk, an optical disk,a magneto-optical disk, or a semiconductor memory.

In the computer configured as described above, the CPU 101 loads aprogram stored in the storage block 108 into the RAM 103 via theinput/output interface 105 and the bus 104 to run the loaded program,thereby executing the above-mentioned sequence of processing operations.

It should be noted that the program to be run by the computer mayexecute the processing operations in a time dependent manner in thesequence described herein, in parallel, or as on an on-demand basis.

It should also be noted that each program may be run by one unit ofcomputer or by two or more units of computers in a distributed manner.Further, each program may be transferred to a remote computer and runthereon.

It should also be noted that term “system” as used herein denotes anentire apparatus configured by a plurality of component units.

While preferred embodiments of the present invention have been describedusing specific terms, such description is for illustrative purpose, andit is to be understood that changes and variations may be made withoutdeparting from the spirit or scope of the following claims.

What is claimed is:
 1. A transmission apparatus for transmitting AV(Audio/Video) content, comprising: acquisition means for acquiring anestimated number of audience terminals indicative of an estimated numberof reception apparatuses receiving said AV content; computation meansfor, in conjugation with said AV content, computing, on the basis ofsaid estimated number of audience terminals, a validity probability oftrigger information associated with control of an application program tobe executed in said reception apparatus; generation means for generatingsaid trigger signal including said computed validity probability; andtransmission means for transmitting said generated trigger informationwith said AV content.
 2. The transmission apparatus according to claim1, wherein said generation means generates, including said computedvalidity probability, trigger information for controlling, in saidreception apparatus, at least one of processing of acquiring saidapplication program, processing of launching said acquired applicationprogram, processing of event firing in said active application program,processing of suspending said active application program, and processingof terminating said active application program.
 3. The transmissionapparatus according to claim 2, wherein said generation means generates,including said computed validity probability, said trigger informationfor controlling, in said reception apparatus, at least one of processingof acquiring said application program that involves processing ofaccessing a predetermined server and processing of event firing in saidactive application program.
 4. The transmission apparatus according toclaim 1, wherein said acquisition means acquires said estimated numberof audience terminals on the basis of past viewing statistics.
 5. Thetransmission apparatus according to claim 3, wherein said acquisitionmeans acquires said estimated number of audience terminals on the basisof actual measurements of access to said server.
 6. A transmissionmethod for a transmission apparatus for transmitting AV (AudioNideo)content, comprising the steps of: acquiring, by said transmissionapparatus, an estimated number of audience terminals indicative of anestimated number of reception apparatuses receiving said AV content;computing, by said transmission apparatus, in conjugation with said AVcontent, on the basis of said estimated number of audience terminals, avalidity probability of trigger information associated with control ofan application program to be executed in said reception apparatus;generating, by said transmission apparatus, said trigger informationincluding said computed validity probability; and transmitting, by saidtransmission apparatus, said generated trigger information with said AVcontent.
 7. A program for controlling a transmission apparatus fortransmitting AV (Audio/Video) content, said program causing a computerof said transmission apparatus to execute processing comprising thesteps of: acquiring an estimated number of audience terminals indicativeof an estimated number of reception apparatuses receiving said AVcontent; computing, in conjugation with said AV content, on the basis ofsaid estimated number of audience terminals, a validity probability oftrigger information associated with control of an application program tobe executed in said reception apparatus; generating said triggerinformation including said computed validity probability; andtransmitting said generated trigger information with said AV content. 8.A reception apparatus for receiving transmitted AV (Audio/Video)content, comprising: extraction means for extracting trigger informationassociated with control of an application program, transmitted with saidAV content, to be executed in conjugation with said AV content;determination means for determining whether said trigger information isvalid on the basis of a validity probability included in said extractedtrigger information; and control means for controlling processingassociated with said application program in response to a commandindicated by said extracted trigger information only when said triggerinformation is determined to be valid.
 9. The reception apparatusaccording to claim 8, wherein said control means controls at least oneof processing of acquiring said application program, processing oflaunching said acquired application program, processing of event firingin said active application program, processing of suspending said activeapplication program, and processing of terminating said activeapplication program in accordance with a command indicated by saidextracted trigger information only when said trigger information isdetermined to be valid.
 10. The reception apparatus according to claim9, wherein said control means controls at least one of processing ofacquiring said application program that involves processing of accessinga predetermined server and processing of event firing in said activeapplication program in accordance with a command indicated by saidextracted trigger information only when said trigger information isdetermined to be valid.
 11. A reception method for a reception apparatusfor receiving transmitted AV (Audio/Video) content, comprising the stepsof: extracting, by said reception apparatus, trigger informationassociated with control of an application program, transmitted with saidAV content, to be executed in conjugation with said AV content;determining, by said reception apparatus, whether said triggerinformation is valid on the basis of a validity probability included insaid extracted trigger information; and controlling, by said receptionapparatus, processing associated with said application program inresponse to a command indicated by said extracted trigger informationonly when said trigger information is determined to be valid.
 12. Aprogram for controlling a reception apparatus for receiving transmittedAV (Audio/Video) content, said program causing a computer of saidreception apparatus to execute processing comprising the steps of:extracting trigger information associated with control of an applicationprogram, transmitted with said AV content, to be executed in conjugationwith said AV content; determining whether said trigger information isvalid on the basis of a validity probability included in said extractedtrigger information; and controlling processing associated with saidapplication program in response to a command indicated by said extractedtrigger information only when said trigger information is determined tobe valid.
 13. A broadcasting system comprising: a transmission apparatusfor transmitting AV (AudioNideo) content; and a reception apparatus forreceiving said AV content transmitted from said transmission apparatus,wherein said transmission apparatus has acquisition means for acquiringan estimated number of audience terminals indicative of an estimatednumber of reception apparatuses receiving said AV content, computationmeans for, in conjugation with said AV content, computing, on the basisof said estimated number of audience terminals, a validity probabilityof trigger information associated with control of an application programto be executed in said reception apparatus, generation means forgenerating said trigger information including said computed validityprobability, and transmission means for transmitting said generatedtrigger information with said AV content; and said reception apparatushas extraction means for extracting trigger information transmitted withsaid AV content, to be executed in conjugation with said AV content,determination means for determining whether said trigger information isvalid on the basis of a validity probability included in said extractedtrigger information, and control means for controlling processingassociated with said application program in response to a commandindicated by said extracted trigger information only when said triggerinformation is determined to be valid.
 14. A transmission apparatus fortransmitting AV (AudioNideo) content, comprising: an acquirer configuredto acquire an estimated number of audience terminals indicative of anestimated number of reception apparatuses receiving said AV content; acomputer configured, in conjugation with said AV content, to compute, onthe basis of said estimated number of audience terminals, a validityprobability of trigger information associated with control of anapplication program to be executed in said reception apparatus; agenerator configured to generate said trigger signal including saidcomputed validity probability; and a transmitter configured to transmitsaid generated trigger information with said AV content.
 15. A receptionapparatus for receiving transmitted AV (Audio/Video) content,comprising: an extractor configured to extract trigger informationassociated with control of an application program, transmitted with saidAV content, to be executed in conjugation with said AV content; adeterminator configured to determine whether said trigger information isvalid on the basis of a validity probability included in said extractedtrigger information; and a controller configured to control processingassociated with said application program in response to a commandindicated by said trigger information in accordance with a validityprobability included in said extracted trigger information only whensaid trigger information is determined to be valid.